Mitigating Crack Propagation in a Highly Maneuverable Flight Vehicle Using Life Extending Control Logic

In this research, life extending control logic is proposed to reduce the cost of treating the aging problem of military aircraft structures and to avoid catastrophic failures and fatal accidents due to undetected cracks in the airframe components. The life extending control logic is based on load tailoring to facilitate a desired stress sequence that prolongs the structural life of the cracked airframe components by exploiting certain nonlinear crack retardation phenomena. The load is tailored to include infrequent injections of a single-cycle overload or a single-cycle overload and underload. These irregular loadings have an anti-intuitive but beneficial effect, which has been experimentally validated, on the extension of the operational structural life of the aircraft. A rigid six-degree-of freedom dynamic model of a highly maneuverable air vehicle coupled with an elastic dynamic wing model is used to generate the stress history at the lower skin of the wing. A three-dimensional equivalent plate finite element model is used to calculate the stress in the cracked skin. The plate is chosen to be of uniform chord-wise and span-wise thickness where the mechanical properties are assigned using an ad-hoc approach to mimic the full scale wing model. An in-extensional 3-node triangular element is used as the gridding finite element while the aerodynamic load is calculated using the vortex-lattice method where each lattice is laid upon two triangular finite elements with common hypotenuse. The aerodynamic loads, along with the base-excitation which is due to the motion of the rigid aircraft model, are the driving forces acting on the wing finite element model. An aerodynamic control surface is modulated based on the proposed life extending control logic within an existing flight control system without requiring major modification. One of the main goals of life extending control logic is to enhance the aircraft\u27s service life, without incurring significant loss of vehicle dynamic performance. The value of the control-surface deflection angle is modulated so that the created overstress is sufficiently below the yield stress of the panel material. The results show that extension in crack length was reduced by 40% to 75% with an absence of damage mitigation logic. Moreover, the desired structural integrity is satisfied without affecting the air vehicle dynamic performance

UTJECAJ DULJINE IGS BAZE NA TOČNOST POZICIONIRANJA GNSS-A

Since the establishment of the International GNSS Service (IGS) stations, they have been used as control stations for assigning the Precise point positioning (PPP) positions using one Global Navigation Satellite System (GNSS) receiver, which has increased from day-to-day. There are some factors affecting the accuracy of PPP positioning. This research aims to investigate the relation between the IGS distance and observed field points as well as to attempt to describe that relation mathematically/statically. For the realization of that aim, two field points are fixed inside the Assiut University campus and observed successively for a session of 24 hour observation. The position of each field point is assigned with the help of each one of the available IGS station products. It must be known that these products are found after observations in three files (IGU, IGR, and final IGS), whereas IGU is used directly as real-time data (ultra-rapid), IGR (rapid) is used through (17-41 hours) after observation, and (final IGS) used after 12 – 18 days. Coordinates and point errors of each field points are computed and represented. It has been found that the errors have a positive relation with the available IGS stations distances. The relation between these distances and point positioning errors have been represented and described according to a model. The accuracy of the presented model is (R ≅ .98, x2 ≅ 2.5 × 10-3).Od uspostave postaja Međunarodnoga GNSS servisa (IGS) iz dana u dan povećava se korištenje kontrolnih stanica za dodjelu položaja precizne točke (PPP) pomoću jednoga prijamnika Globalnoga satelitskog navigacijskog sustava (GNSS). Postoje neki čimbenici koji utječu na točnost PPP pozicioniranja. Cilj je ovoga istraživanja istražiti odnos između IGS udaljenosti i promatranih točaka polja te opisati taj odnos matematički i statički. Za realizaciju toga cilja dvije terenske točke fiksirane su unutar kampusa Sveučilišta Assiut i promatrane sukcesivno tijekom sesije promatranja od 24 sata. Položaj svake točke polja dodjeljuje se uz pomoć svakoga od dostupnih proizvoda IGS stanica. Bitno je napomenuti da se ti produkti nalaze u tri datoteke (IGU, IGR i konačni IGS) nakon promatranja, dok se IGU koristi izravno kao podatci u stvarnome vremenu (ultra-rapid), IGR (rapid) kroz 17 – 41 sat nakon promatranja, a konačni IGS nakon 12 – 18 dana. Koordinate i pogreške točaka svake točke polja izračunane su i prikazane. Utvrđeno je da su pogreške u pozitivnom odnosu s dostupnim udaljenostima IGS postaja. Odnos između tih udaljenosti i pogrešaka pozicioniranja točke prikazan je i opisan prema modelu. Točnost je prikazanoga modela R ≅ .98, x2 ≅ 2.5 × 10-3

Studying the Effect of Potassium Amyl Xanthate Surfactant on Fe, Cu and U Ions for the Pretreatment of Abu Zeneima Sulphate Leach Liquor

In this study, batch experiments were performed to study the behavior of potassium amyl xanthate surfactant on Fe, Cu and U ions for the pretreatment of Abu Zeneima sulphate leach liquor. Various parameters, such as amount of potassium amyl xanthate, pH, stirring time, sample volume to potassium amyl xanthate mass (v/m ratio) and temperature were tested to determine the optimum conditions. The numerical results obtained support the experimental data on decreasing the iron and copper values where 0.1 g potassium amyl xanthate could remove 86.8 mg Fe and 0.98 mg Cu from the studied sulphate solution with no effect on uranium content. FTIR spectroscopy and XRF analysis were used for investigation

The chemical composition and in vitro digestibility evaluation of almond tree (Prunus dulcis D. A. Webb syn. Prunus amygdalus; var. Shokoufeh) leaves versus hulls and green versus dry leaves as feed for ruminants

The current study aimed to evaluate the chemical composition and in vitro digestibility of almond tree (Prunus dulcis D. A. Webb syn. Prunus amygdalus; var. Shokoufeh) leaves versus hulls, and green versus dry leaves as feed for ruminants. The fresh green almond hulls (GAH) and leaves (GAL) were harvested and spread under a shade to dry. Dry almond leaves (DAL) were collected from under the trees where as dry almond hulls (DAH) were collected 4 weeks after harvesting the fresh samples. The chemical composition of substrates was determined using standard approaches and the metabolisable energy (ME), in vitro dry matter (DMD) and in vitro organic matter (OMD) digestibility were measured using the in vitro gas production (GP) technique. The GAL contained 81 g crude protein (CP) kg-1 DM while DAH contained 103 g CP kg-1 DM. The CP was higher (P = 0.0003) in dry (leaves and hulls) than in green (leaves and hulls) samples. The ash content ranged from 99.2 to 181.5 g kg-1 DM in DAH and DAL, respectively, (P = 0.0041). The ether extract content ranged from 27 for DAH to 65 g kg-1 for DAL (P = 0.0018). The acid detergent fibre and neutral detergent fibre content ranged from 185 to 304 and 444 to 620 g kg-1 DM (P = 0.04), for GAL and DAH, respectively. The DAH had the highest (P = 0.0001) GP24 and GP96. The DAH had the highest (P = 0.0001) potential GP (i.e., b), while the GP rate was highest for GAL and GAH (P = 0.034), ME was highest for DAH (P = 0.0001), and in vitro OMD was highest for DAH (P = 0.0001). The highest DMD (P = 0.0001) values were obtained with DAH followed by GAL, DAL and GAH, respectively. It can be concluded that almond hulls and leaves have a good nutritional potential to cover the maintenance nutrient requirements of small ruminants. Almond hulls and leaves can also be used as supplement to low quality mature pasture and/or crop residues. However, more studies are warranted to better characterize these feeds in in vivo animal feeding trials

A ring-connected dual active bridge based DC-DC multiport converter for EV fast-charging stations

This paper proposes a multiport DC-DC converter for EV fast-charging stations. The proposed converter is comprised of Ring-Connected Dual Active Bridge (RCDAB) DC-DC converters, where the connection point between every two adjacent DABs provides a DC port. Bypass switches are added to each DAB to eliminate unnecessary power processing stages in the event of idle ports (no EVs) (open circuit ports). The nature of the ring connection of the RCDAB theoretically allows infinite internal power flow solutions within the ring to satisfy a certain power flow scenario at the DC ports, hence, the optimal power flow solution can be selected to minimize total RMS current and losses. Single-phase shift control is applied to this optimization problem to make it simple. A novel closed-loop control scheme using Bisection optimization is developed to minimize the total RMS current. A control-hardware-in-the-loop (CHiL) validation is carried out for a 5-port network of the proposed topology to investigate the converter efficiency and fault tolerance/availability characteristics. Also, an experimental hardware validation is implemented for a 3-port network where different scenarios for power flow and faults are performed. Finally, a comparative discussion between the proposed topology and other multiport topologies in literature is presented revealing the superior performance of the RCDAB topology

The chemical composition and in vitro digestibility evaluation of almond tree (Prunus dulcis D. A. Webb syn. Prunus amygdalus; var. Shokoufeh) leaves versus hulls and green versus dry leaves as feed for ruminants

Almond, (Prunus dulcis D. A. Webb syn. Prunus amygdalus) is a species belonging to the Rosaceae family (Sfahlan et al. 2009). The state of California in the USA is the major producer of almond; however, its production is widely distributed (Wijerante et al. 2006) and there is increasing interest to produce almond and its by-products worldwide. Approximately 2,112,815 metric ton of almonds with shell is produced globally with Iran contributing about 110,000 metric ton (FAO 2007). Almond is a midsize tree with fruit that can grow up to ten meters tall (Chen et al. 2010). The fruit is made of hulls, shell and kernel. Drying almond hulls results in approximately (kg-1 DM) 250 g nut, 500 g hulls and 250 g shell (Aguilar et al. 1984; Fadel 1999).The current study aimed to evaluate the chemical composition and in vitro digestibility of almond tree (Prunus dulcis D. A. Webb syn. Prunus amygdalus; var. Shokoufeh) leaves versus hulls, and green versus dry leaves as feed for ruminants. The fresh green almond hulls (GAH) and leaves (GAL) were harvested and spread under a shade to dry. Dry almond leaves (DAL) were collected from under the trees where as dry almond hulls (DAH) were collected 4 weeks after harvesting the fresh samples. The chemical composition of substrates was determined using standard approaches and the metabolisable energy (ME), in vitro dry matter (DMD) and in vitro organic matter (OMD) digestibility were measured using the in vitro gas production (GP) technique. The GAL contained 81 g crude protein (CP) kg-1 DM while DAH contained 103 g CP kg-1 DM. The CP was higher (P = 0.0003) in dry (leaves and hulls) than in green (leaves and hulls) samples. The ash content ranged from 99.2 to 181.5 g kg-1 DM in DAH and DAL, respectively, (P = 0.0041). The ether extract content ranged from 27 for DAH to 65 g kg-1 for DAL (P = 0.0018). The acid detergent fibre and neutral detergent fibre content ranged from 185 to 304 and 444 to 620 g kg-1 DM (P = 0.04), for GAL and DAH, respectively. The DAH had the highest (P = 0.0001) GP24 and GP96. The DAH had the highest (P = 0.0001) potential GP (i.e., b), while the GP rate was highest for GAL and GAH (P = 0.034), ME was highest for DAH (P = 0.0001), and in vitro OMD was highest for DAH (P = 0.0001). The highest DMD (P = 0.0001) values were obtained with DAH followed by GAL, DAL and GAH, respectively. It can be concluded that almond hulls and leaves have a good nutritional potential to cover the maintenance nutrient requirements of small ruminants. Almond hulls and leaves can also be used as supplement to low quality mature pasture and/or crop residues. However, more studies are warranted to better characterize these feeds in in vivo animal feeding trials

Effect of polyethylene glycol on in vitro gas production kinetics of Prosopis cineraria leaves at different growth stages

The aim of this experiment was to determine the effect of polyethylene glycol (PEG) on in vitro gas production (GP) kinetics of Prosopis cineraria leaves at different growth stages. The contents of total phenol (TPH), total tannin (TT) and condensed tannin (CT) were determined. Effects on in vitro organic matter digestibility (OMD), metabolisable energy (ME) and effective dry matter digestibility were assessed by PEG tannin bioassay. No significant differences (P>0.05) were observed for TPH content; however, the stage of flowering had the highest (P0.05) were observed between the growth stage and PEG addition for in vitro GP and its parameters. Addition of PEG increased (P<0.05) GP, OMD and ME in all stages. In conclusion, adding PEG to P. cineraria leaves can improve their nutritive value and could be considered as a potential feed for ruminants

Work stress, work-family conflict, and psychological distress among resort employees: a JD-R model and spillover theory perspectives

The hospitality industry is well-known for its challenging and high-pressure work settings. In this context, employees commonly face a multitude of stressors originating from their roles and job responsibilities, which can significantly impact their psychological wellbeing. Hence, based on the job demands-resources (JD-R) model and the spillover theory, this study aims to empirically explore the direct and indirect effect of work stress (assessed by role overload, ambiguity, and conflict) on psychological distress among frontline employees in 3- and 4-star Egyptian resorts while considering the mediating influence of work-family conflict (WFC). Four hypotheses were put to the test through the application of the PLS-SEM 4.0 version (4.0.9.9). Based on the findings from 563 frontline employees who participated in this research, the study supports the four hypotheses affirming that work-related stressors significantly contributed to employees' psychological distress. Further, the findings highlighted that these stressors significantly spill over into employees' family lives, generating conflicts between work and family roles. In addition, the results emphasized the significance of WFC as a contributing factor to employees' psychological distress. Finally, the study concluded that WFC partially mediates the link between work stress and employees' psychological distress. Based on these findings, some theoretical and practical implications for hospitality scholars, resort management, and policymakers were suggested to enhance the employees' wellbeing and mitigate psychological distress in this vital sector

Functional Recellularization of Acellular Rat Liver Scaffold by Induced Pluripotent Stem Cells: Molecular Evidence for Wnt/B-Catenin Upregulation.

BACKGROUND: Liver transplantation remains the only viable therapy for liver failure but has a severely restricted utility. Here, we aimed to decellularize rat livers to form acellular 3D bio-scaffolds suitable for seeding with induced pluripotent cells (iPSCs) as a tool to investigate the role of Wnt/β-catenin signaling in liver development and generation. METHODS: Dissected rat livers were randomly divided into three groups: I (control); II (decellularized scaffolds) and III (recellularized scaffolds). Liver decellularization was established via an adapted perfusion procedure and assessed through the measurement of extracellular matrix (ECM) proteins and DNA content. Liver recellularization was assessed through histological examination and measurement of transcript levels of Wnt/β-catenin pathway, hepatogenesis, liver-specific microRNAs and growth factors essential for liver development. Adult rat liver decellularization was confirmed by the maintenance of ECM proteins and persistence of growth factors essential for liver regeneration. RESULTS: iPSCs seeded rat decellularized livers displayed upregulated transcript expression of Wnt/β-catenin pathway-related, growth factors, and liver specification genes. Further, recellularized livers displayed restored liver-specific functions including albumin secretion and urea synthesis. CONCLUSION: This establishes proof-of-principle for the generation of three-dimensional liver organ scaffolds as grafts and functional re-establishment

Antimicrobial resistance among migrants in Europe: a systematic review and meta-analysis

BACKGROUND: Rates of antimicrobial resistance (AMR) are rising globally and there is concern that increased migration is contributing to the burden of antibiotic resistance in Europe. However, the effect of migration on the burden of AMR in Europe has not yet been comprehensively examined. Therefore, we did a systematic review and meta-analysis to identify and synthesise data for AMR carriage or infection in migrants to Europe to examine differences in patterns of AMR across migrant groups and in different settings. METHODS: For this systematic review and meta-analysis, we searched MEDLINE, Embase, PubMed, and Scopus with no language restrictions from Jan 1, 2000, to Jan 18, 2017, for primary data from observational studies reporting antibacterial resistance in common bacterial pathogens among migrants to 21 European Union-15 and European Economic Area countries. To be eligible for inclusion, studies had to report data on carriage or infection with laboratory-confirmed antibiotic-resistant organisms in migrant populations. We extracted data from eligible studies and assessed quality using piloted, standardised forms. We did not examine drug resistance in tuberculosis and excluded articles solely reporting on this parameter. We also excluded articles in which migrant status was determined by ethnicity, country of birth of participants' parents, or was not defined, and articles in which data were not disaggregated by migrant status. Outcomes were carriage of or infection with antibiotic-resistant organisms. We used random-effects models to calculate the pooled prevalence of each outcome. The study protocol is registered with PROSPERO, number CRD42016043681. FINDINGS: We identified 2274 articles, of which 23 observational studies reporting on antibiotic resistance in 2319 migrants were included. The pooled prevalence of any AMR carriage or AMR infection in migrants was 25·4% (95% CI 19·1-31·8; I2 =98%), including meticillin-resistant Staphylococcus aureus (7·8%, 4·8-10·7; I2 =92%) and antibiotic-resistant Gram-negative bacteria (27·2%, 17·6-36·8; I2 =94%). The pooled prevalence of any AMR carriage or infection was higher in refugees and asylum seekers (33·0%, 18·3-47·6; I2 =98%) than in other migrant groups (6·6%, 1·8-11·3; I2 =92%). The pooled prevalence of antibiotic-resistant organisms was slightly higher in high-migrant community settings (33·1%, 11·1-55·1; I2 =96%) than in migrants in hospitals (24·3%, 16·1-32·6; I2 =98%). We did not find evidence of high rates of transmission of AMR from migrant to host populations. INTERPRETATION: Migrants are exposed to conditions favouring the emergence of drug resistance during transit and in host countries in Europe. Increased antibiotic resistance among refugees and asylum seekers and in high-migrant community settings (such as refugee camps and detention facilities) highlights the need for improved living conditions, access to health care, and initiatives to facilitate detection of and appropriate high-quality treatment for antibiotic-resistant infections during transit and in host countries. Protocols for the prevention and control of infection and for antibiotic surveillance need to be integrated in all aspects of health care, which should be accessible for all migrant groups, and should target determinants of AMR before, during, and after migration. FUNDING: UK National Institute for Health Research Imperial Biomedical Research Centre, Imperial College Healthcare Charity, the Wellcome Trust, and UK National Institute for Health Research Health Protection Research Unit in Healthcare-associated Infections and Antimictobial Resistance at Imperial College London